Get first element Xpath - node.js

Question

I have a HTML like this :
<ol class="list">
<li class="list-item " id="37647629">
<!---->
<div>
<!---->
<div>
<!---->
<book class="book">
<div class="title">
someText
</div>
<div class="year">
2022
</div>
</book>
</div>
<!---->
</div>
<!---->
</li>
<li class="list-item " id="37647778">
<!---->
<div>
<!---->
<div>
<!---->
<book class="book">
<div class="title">
someOtherText
</div>
<div class="year">
2014
</div>
</book>
</div>
</div>
<!---->
</li>
</ol>
I want to get the first book title and year, directly with two xPath expression.
I tried :
$x('//book') => Ok, get the two books list
$x('//book[0]') => Empty list
$x('//book[0]/div[#class="title"]') => Nothing
Seems I have to do this :
$x('//book')[0]
and then process title, but why I can't do this just with Xpath and directly access the first title with a Xpath expression ?

Answer 1

This will give you the first book title
"(//book)[1]//div[#class='title']"
And this gives the first book year
"(//book)[1]//div[#class='year']"

Answer 2

You're missing that XPath indexing starts at 1; JavaScript indexing starts at 0.
$x('//book') selects all book elements in the document.
$x('//book[0]') selects nothing because XPath indexing starts at 1. (It also signifies to select all book elements that are the first among siblings — not necessarily the same as the first of all book elements in the document.)
$x('//book')[0] would select the first book element because JavaScript indexing starts at 0.
$x('(//book)[1]') would select the first book element because XPath indexing starts at 1.
To select the first div with class of 'title', all in XPath:
$x('(//div[#class="title"])[1]')
or, using JavaScript to index:
$x('(//div[#class="title"])')[0]
To return just the string value without the leading/trailing whitespace, wrap in normalize-space():
$x('normalize-space((//div[#class="title"])[1])')
Note that normalize-space() will also consolidate internal whitespace, but that is of no consequence with this example.
See also
How to select first element via XPath? (And be sure not to miss the explanation of the difference between //book[1] and (//book)[1] — they are not the same.)